An automatic filter network failure detection and correction system is known in the prior art, namely that disclosed in U.S. Pat. No. 4,356,007 to H. L. Bowman, Oct. 26, 1982. Thus, increased fluid flow through individual filter bags caused by holes in the bag fabric is detected to operate a valving mechanism to close off that individual bag and thus prevent leakage of raw fluid with pollutants into the atmosphere. This invention is related to that general type of detection and correction system.
There are many problems encountered in sensing and controlling bag failures in these "baghouse" filtering systems that have not been recognized or corrected by prior art systems. For example the flow of fluids through filtering systems creates zones of turbulence, eddies, laminar flow, calm and other flow conditions that may be dynamically changing with volume and velocity of flow or be rather static due to flow path characteristics. These flow patterns not only affect the life of filters, but more important they affect, the ability to detect changes in flow volume at particular detector locations, and the ability to use flow volume characteristics to automatically operate vents or valves in automatic control systems. Thus, automatic capping of leaking bags, by sensing and employing changes in flow volume, becomes critical in the presence of variations of operating conditions, which as a practical matter is a necessity in most installations that do not have constantly regulated unchanging flow conditions.
Furthermore because of the necessity to retrofit existing systems for refining improvements as environmental standards become stricter, any automatic system for capping of leaking bags cannot be designed for optimal performance under unknown future conditions. Also, the points of access into the bag systems for installation of sensors and cappers are limited, and tend to be in positions encountering high turbulence such as in plenum areas, and the like.
In some systems, flow changes are so extreme in nature that flow detectors and flow controlling valves may be operated erratically to defeat the purpose of eliminating more pollution. Thus for example, in jet pulse type self cleaning systems, the air flow reverses in direction and involves violent jet pulses or rhythmic vibrations inconsistent with operation of detectors and controllers required for pollution control.
Also the automation of systems is sometimes limited because the controllers are "hidden" in the system in spots that are difficult to monitor so that problems are hard to detect when bags begin to fail. For each bag that is capped off, for example, an additional stress is placed upon remaining bags to handle the flow load. Thus, careful monitoring of the number of capped off bags is essential by monitoring the differential pressure across the compartment. Also dynamic monitoring is desirable to determine the nature, frequency and positions of failures so that related causes may be quickly corrected before the atmosphere is polluted by filter system failure.
Another critical condition under which atmospheric pollution may occur is in the initial installation of new bag filters. The flow of air through new bags tends to be much less restricted until they develop a dust caking that limits flow. Thus flow is diverted from caked bags into a bank or section having new bags, which can result in catastrophic failure or pollution flow into the atmosphere that is normally filtered out by help of the dust caking which builds up in due course.
Furthermore turbulence in flow at the entryway into the bags can cause excessive wear at the bag "cuff" because of concentration of abrasive particles directed toward the fabric rather than in laminar flow paths for which the systems are designed.
Therefore, it is to be recognized that many critical conditions are imposed upon automatic sensing and flow control systems for capping ruptured filter bags to prevent loss of pollution into the atmosphere, of a nature not addressed or resolved in prior art systems.
It is therefore an objective of this invention to provide an improved automatic pollution control system for capping off ruptured baghouse filter bags which resolves these problems and deficiencies of prior art systems.
Other objects, features and advantages of the invention will be found throughout the following description, drawings and claims.